Conventionally, a pulverizer including a spray nozzle spraying airstream and a pulverization chamber (fluid bed) in which a subject is pulverized by the airstream, i.e., a fluidized bed pulverizer is known. The pulverizer includes plural spray nozzles, and the subject collides to each other at a space where the airstreams sprayed from the plural spray nozzles meet each other and is pulverized by the collision energy. The pulverized subject is classified to obtain particles having a desired particle diameter.
Japanese Patent No. 3984120 discloses fitting a cylindrical adaptor to the spray nozzle for the purpose of increasing directivity of the airstream sprayed from the spray nozzle. The cylindrical adaptor includes a flow path the airstream sprayed from a front end face of the spray nozzle passes through. An inlet hole inhaling the pulverized subject in the pulverization chamber into the follow path is located on the side wall thereof.
The cylindrical adaptor inhales the pulverized subject in the pulverization chamber into the follow path through the inlet hole due to an ejector effect of the airstream flowing through the flow path. The pulverized subject inhaled into the flow path is accelerated by the airstreams flowing through the flow path and sprayed from an exit of the cylindrical adaptor to the space where the airstreams meet each other.
The cylindrical adaptor increases directivity of the airstream sprayed from the front end face of the spray nozzle and a subject to be pulverized has high density at the space where the plural airstreams meet each other. Therefore, the pulverization efficiency is improved.
FIG. 9 is a schematic view illustrating conventional spray nozzle and cylindrical adaptor. As FIG. 9 shows, a front end face 114 of the spray nozzle 110 has a tapered surface 112 facing forward. In addition, when a cylindrical adaptor 120 is fitted to the spray nozzle 110, a rear end face 124 of an inlet hole 122 is located behind the front end face 114 of the spray nozzle 110.
However, the ejector effect is not sufficiently obtained when the rear end face 124 of the inlet hole 122 is located behind the front end face 114 of the spray nozzle 110.
Therefore, there is a space where the pulverized subject is inhaled at low speed near the tapered surface 112 of the spray nozzle 110. Consequently, the flow of the pulverized subject stagnates and acceleration efficiency thereof is low, resulting in low pulverization efficiency.
Because of these reasons, a need exists for a pulverizer and a cylindrical adaptor having good pulverization efficiency.